World-leading technology company ARM Holdings said a vote to leave the European Union by the British electorate, the so-called Brexit, would hinder its ability to employ the scientists and engineers it needs.

ARM, which designs the chips that power nearly all of the world's smartphones including Apple's iPhone and Samsung's top models, is the most valuable tech company listed in London.

Around 300 of its employees in Cambridge, some 10 percent of its highly skilled workforce, came from mainland Europe, Chief Finance Officer Chris Kennedy said on Wednesday.

"Our main concern is the ability to attract talent and be able to get the necessary papers for them to work in the UK in the event of Brexit," he said, after the company reported higher fourth-quarter profits.

"It would slow us down."

It is unclear what the consequences of a British exit would be, including whether it would lead to the introduction of visas for workers from EU member states.

Britain's Prime Minister David Cameron has promised voters an opportunity to decide whether the country should remain a member of the European Union in a referendum that could happen as soon as June.

Cameron is trying to win a new deal for Britain in the trading bloc, including the return of some powers to London from Brussels and curbs on benefits payments to workers from continental Europe, before a vote promised by the end of 2017.